AFO Types and Considerations

Question 1

Solid or Rigid

Answer 1

Provides rigid support of ankle in desired position that has implications for knee control

Question 2

Solid or Rigid Benefits

Answer 2

1. Increased Dorsiflexion swing
2. Adjustability of stiffness by changing trimlines
3. Increased stance phase; knee flexion or extension by restricting ankle motion
4. Decreased equinovarus in stance
5. Possible ankle control with PF spasticity
6. Increased static balance

Question 3

Solid or rigid: considerations that may limit success

Answer 3

1. Desire to allow volitional muscle activation
2. Decrease PROM
   3 Bulk and weight of AFO
3. Desire for allowing ankle DF during functional mobility

Question 4

Solid or rigid: Key AFO design considerations

Answer 4

1. Material strength provides increased motion restriction and ankle control
2. Increased AFO stiffness may lead to increased knee flexion at IC
3. Anterior trimlines increased ankle control
4. AFO rigidity AFO set in DF leads to knee flexion in stance
5. AFO set in PF leads to knee extension in stance
6. Increased AFO stiffness may increase knee flexion at IC

Question 5

Solid AFO Example

Answer 5

1. Anterior trimlines
2. Thicker materials
3. Fixed at ankle in slight PF, neutral, or DF based on control needed

Question 6

Ground Reaction

Answer 6

Provides knee stability through a posteriorly directed force on the proximal tibia

Question 7

Ground Reaction: Benefits

Answer 7

1. Increased DF in swing
2. Strong stance phase knee flexion control
3. Possible increased gait speed if a soft heel or rocker sole is added to the shoe
4. Increased static balance

Question 8

Ground Reaction: Considerations that may limit success

Answer 8

1. Genu recurvatum
2. Strong hyperextension thrust in stance
3. Quadriceps spasticity
4. bulk and weight of AFO

Question 9

Ground Reaction: Key AFO design considerations

Answer 9

1. Anterior proximal contact of AFO leads to stance phase knee extension
2. Increased AFO stiffness may increased knee flexion at IC
3. AFO set in PF leads to knee extension in stance

Question 10

Ground Reaction AFO Example

Answer 10

1. Fixed at ankle in slight PF
2. Anterior shell for added tibial control
3. Carbon or plastic options

Question 11

Semirigid

Answer 11

Provides varying degrees of rigidity based on design and materials used

Question 12

Semirigid: Benefits

Answer 12

1. Increased DF in swing
2. Adjustability of stiffness by changing trimlines
3. Increased stance phase knee flexion or extension by limiting ankle motion
4. Increased gait speed if AFO has fewer restrictions to movement
5. May increased dynamic balance based on design

Question 13

Semirigid: Considerations that may limit success

Answer 13

1. PF spasticity (great or equal to MAS 3)
2. Decreased strength or control of the ankle or knee muscles
3. Equinovarus

Question 14

Semirigid: Key AFO considerations

Answer 14

1. Material roperty choices restrict or allow motion
2. AFO set in DF leads to knee flexion in stance
3. AFO set in PF leads to knee extension in stance
4. Anterior trimlines increase ankle control and AFO rigidity
5. Posterior trimlines decrease ankle control and AFO rigidity

Question 15

Semirigid AFO Example

Answer 15

1. More posterior trimlines
2. Ankle in slight PF, neutral, or DF based on control needed
3. Some ankle motion allowed based on material thickness and flexibility

Question 16

Flexible/Posterior Leaf Spring

Answer 16

Provides varying degrees of flexibility based on design and materials used

Question 17

Flexible/Posterior Leaf Spring: Benefits

Answer 17

1. Increased DF in swing
2. Lightweight
3. Pre-fabricated options
4. Increased gait speed

Question 18

Flexible/Posterior Leaf Spring: Considerations that may limit success

Answer 18

1. PF spasticity (great or equal to MAS 3)
2. Decreased strength or control of the ankle or knee muscles
3. Decreased dynamic balnace

Question 19

Flexible/Posterior Leaf Spring: Key AFO Design Considerations

Answer 19

1. Material properties allow motion
2. Posterior trimlines decrease ankle control and AFO rigidity

Question 20

Posterior Leaf Spring AFO Example

Answer 20

1. Most posterior trimline
2. More ankle motion allowed due to material flexibility
3. Minimal to no mediolateral ankle support
4. Minimal to no effect at the knee

Question 21

Articulating

Answer 21

Provides varying degrees of motion at the ankle through hinges with optional stops to limit ROM if desired

Question 22

Articulating: Benefits

Answer 22

1. Increased DF in swing
2. Adjustable as patient’s needs change
3. Allows for volitional muscle activation
4. Increased stance phase knee flexion or extension by allowing or restricting ankle motion
5. Decreased equinovarus in stance with design that encompasses more of the ankle
6. Increased gait speed if AFO has less motion restrictions
7. Increased static balance if AFO has more motion restrictions

Question 23

Articulating: Considerations that may limit success

Answer 23

1. PF spasticity (great or equal to MAS 3)
2. Decreased ankle PROM
3. Bulk and weight of AFO
4. Decreased medial/lateral ankle stability

Question 24

Articulating: Key AFO Design Considerations

Answer 24

1. Hinges allow motion
2. Stops restrict motion
3. AFO set in more DF leads to increased knee flexion in stance
4. AFO set in more PF leads to increased knee extension in stance

Question 25

Articulating AFO Example

Answer 25

Double Metal Upright AFO: 1. DF and PF stops set by adjusting screws/bars in each channel 2. Springs can be added for DF assist 3. Good option with edema and to allow modifications with recovery Articulating Plastic AFO: 1. Many options for hinge types 2. DF and PF stops achieved by straps, hinge types, and/or materials abutting 3. Good option to allow modifications with recovery

Question 26

Dynamic

Answer 26

Enhances or resists ankle motion while allowing some motion and/or energy storage

Question 27

Dynamic: Benefits

Answer 27

1. Increased DF in swing 2. Increased push-off force 3. Allows for volitional muscle activation 4. Possible increased stance phase knee flexion or extension by supporting sagittal plane ankle motion 5. Possible decrease equinovarus in stance with design that encompasses more of the ankle 6. Increased gait speed

Question 28

Dynamic: Considerations that may limit success

Answer 28

1. PF spasticity (great or equal to MAS 3) 2. Equinovarus 3. Knee buckling 4. Genu recurvatum 5. Decreased ankle PROM

Question 29

Dynamic: Key AFO Design Considerations

Answer 29

1. Material property and/or spring choices assist, restrict or allow motion 2. AFO set in DF leads to knee flexion in stance 3. AFO set in PF leads to knee extension in stance

Question 30

Dynamic AFO Example

Answer 30

Carbon Fiber AFO: 1. Stores and releases force for push-off 2. Minimal medial/lateral support at ankle 3. Minimal to no adjustability Articulating AFO, DF Assist: 1. Free DF with some DF assist from this hinge 2. PF stop created by contact of shells posteriorly 3. Pin or longer shells can be used posteriorly for more PF restriction